In general, a computer system includes a storage apparatus which includes LUs, and a server coupled with the storage apparatus. The server transmits an I/O request for inputting/outputting data to/from an LU of the storage apparatus. The storage apparatus receives the I/O request and inputs/outputs data in accordance with the I/O request, to/from the LU specified by the I/O request. An LU is a logical storage device, and it may be also called a logical volume. The LU may be a virtual LU or a real LU. The virtual LU may be, for example, an LU in accordance with thin provisioning or may be an LU in accordance with a storage virtualization technique (an LU obtained by virtualizing a storage resource of a storage apparatus outside the storage apparatus). The real LU is an LU based on a physical storage device (hereinafter referred to as a PDEV). For example, one or more real LUs are formed on the basis of a RAID (Redundant Array of Independent (or Inexpensive) Disks) group configured by multiple PDEVs.
There is such a storage apparatus that includes multiple processors and is able to determine which processor is responsible for I/O to/from which LU. With relation to such a storage apparatus, there is known a technique for changing a processor responsible for an LU according to the load of the processor (for example, see Patent Literature 1).
There is also known a technique in which multiple paths are prepared from a server to an LU, and the load of a network or the load of a port of a storage apparatus is distributed by controlling a path selected from among the multiple paths.